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Two-dimensional (2D) of transition metal dichalcogenides (TMDCs) are potential candidates for thermoelectric (TE) applications due to their unique structural properties. In this paper, we constructed an 2D monolayer TMDCs semiconductor γ-PbSn2(X=S, Se, Te) and first-principles calculations and Boltzmann transport theory are used to study the thermoelectric performance. We found that γ-PbSnX2 had an ultra-high carrier mobility up to 4.04×103 cm2V−1s−1 leading to a metal-like electrical conductivity. Meanwhile, γ-PbSnX2 both have high Seebeck coefficients, resulting in high power-factors, and also shows intrinsic low lattice thermal conductivity of 6-8 W/mK at room temperature. The lower lattice thermal conductivity and high power-factors resulted in excellent thermoelectric performance. The high ZT values of γ-PbSnS2 and γ-PbSnSe2 were as high as 2.65 and 2.96 at 900 K, respectively. The result suggests that the monolayer γ-PbSnX2 are better candidates for excellent thermoelectric performance.

In order to explore the application of nanomaterials in fiber concrete, in this research, the effect of nanomaterials SiO2 on the basalt fiber concrete was studied with experimental analysis methods. The variation values of mechanical properties were calculated respectively. On this basis, the influences of silicon dioxide nanometer and basalt fibers on the mechanical properties of nanosilica silicon dioxide nanometer basalt fiber concrete were studied. Different contents of silicon dioxide nanometer were added to concrete, different contents of basalt fibers were added to concrete, and both were added to concrete. The results showed that adding silicon dioxide nanometer could modify building concrete and significantly improve the mechanical properties of concrete. the increase of silicon dioxide nanometer content of nanomaterials, the strength of concrete showed a trend of first rising and then falling. When silicon dioxide nanometer content was 1.2%, the mechanical strength was the largest. As the contents of basalt fiber increase, concrete strength showed a trend of first increasing and then decreasing. When basalt fiber content was 3kg/m3, it was the optimal content and the concrete strength was the largest. And the mechanical properties of the concrete mixed with silicon dioxide nanometer and basalt fibers were significantly improved.

The baker's yeast

The wild yeast Saccharomyces paradoxus has become a new model in ecology and evolutionary biology. Different lineages of S. paradoxus have been recognized across the world, but the distribution and genetic diversity of the species remain unknown in China, where the origin of its sibling species S. cerevisiae lies. In this study, we investigated the ecological and geographic distribution of S. paradoxus through an extensive field survey in China and performed population genomic analysis on a set of S. paradoxus strains, including 27 strains, representing different geographic and ecological origins within China, and 59 strains representing all the known lineages of the species recognized in the other regions of the world so far. We found two distinct lineages of S. paradoxus in China. The majority of the Chinese strains studied belong to the Far East lineage, and six strains belong to a novel highly diverged lineage. The distribution of these two lineages overlaps ecologically and geographically in temperate to subtropical climate zones in China. With the addition of the new China lineage, the Eurasian population of S. paradoxus exhibits higher genetic diversity than the American population. We observed more possible lineage-specific introgression events from the Eurasian lineages than from the American lineages. Our results expand the knowledge on ecology, genetic diversity, biogeography, and evolution of S. paradoxus.

Heterosis or hybrid vigor is a common phenomenon in plants and animals; however, the molecular mechanisms underlying heterosis remain elusive, despite extensive studies on the phenomenon for more than a century. Here we constructed a large collection of F1 hybrids of Saccharomyces cerevisiae by spore-to-spore mating between homozygous wild strains of the species with different genetic distances and compared growth performance of the F1 hybrids with their parents. We found that heterosis was prevalent in the F1 hybrids at 40°C. A hump-shaped relationship between heterosis and parental genetic distance was observed. We then analyzed transcriptomes of selected heterotic and depressed F1 hybrids and their parents growing at 40°C and found that genes associated with one-carbon metabolism and related pathways were generally up-regulated in the heterotic F1 hybrids, leading to improved cellular redox homeostasis at high temperature. Consistently, genes related with DNA repair, stress responses, and ion homeostasis were generally down-regulated in the heterotic F1 hybrids. Furthermore, genes associated with protein quality control systems were also generally down-regulated in the heterotic F1 hybrids, suggesting a lower level of protein turnover and thus higher energy use efficiency in these strains. In contrast, the depressed F1 hybrids, which were limited in number and mostly shared a common aneuploid parental strain, showed a largely opposite gene expression pattern to the heterotic F1 hybrids. We provide new insights into molecular mechanisms underlying heterosis and thermotolerance of yeast and new clues for a better understanding of the molecular basis of heterosis in plants and animals.

Recent studies on population genomics of Saccharomyces cerevisiae have substantially improved our understanding of the genetic diversity and domestication history of the yeast. However, the origin of the domesticated population of S. cerevisiae and the genomic changes responsible for ecological adaption of different populations and lineages remain to be fully revealed. Here we sequenced 64 African strains from various indigenous fermented foods and forests in different African countries and performed a population genomic analysis on them combined with a set of previously sequenced worldwide S. cerevisiae strains representing the maximum genetic diversity of the species documented so far. The result supports the previous observations that the wild and domesticated populations of S. cerevisiae are clearly separated and that the domesticated population diverges into two distinct groups associated with solid- and liquid-state fermentations from a single ancestor. African strains are mostly located in basal lineages of the two domesticated groups, implying a long domestication history of yeast in Africa. We identified genes that mainly or exclusively occur in specific groups or lineages and genes that exhibit evident group or lineage specific allele distribution patterns. Notably, we show that the homing endonuclease VDE is generally absent in the wild but commonly present in the domesticated lineages of S. cerevisiae. The genes with group specific allele distribution patterns are mostly enriched in functionally similar or related fundamental metabolism processes, including the evolutionary conserved TOR signaling pathway.

The yeast Saccharomyces cerevisiae has been an essential component of human civilization because of its long global history of use in food and beverage fermentation. However, the diversity and evolutionary history of the domesticated populations of the yeast remain elusive. We show here that China/Far East Asia is likely the center of origin of the domesticated populations of the species. The domesticated populations form two major groups associated with solid- and liquid-state fermentation and appear to have originated from heterozygous ancestors, which were likely formed by outcrossing between diverse wild isolates primitively for adaptation to maltose-rich niches. We found consistent gene expansion and contraction in the whole domesticated population, as well as lineage-specific genome variations leading to adaptation to different environments. We show a nearly panoramic view of the diversity and life history of S. cerevisiae and provide new insights into the origin and evolution of the species., An understanding of the domestication of the yeast Saccharomyces cerevisiae has important implications for studying its evolution and diversity. Here, the authors show that Far East Asia is likely the center of origin of the domesticated populations of the yeast based on genomic and phenotypic characterization of a large collection of isolates.

Micromilling mechanism studies are the fundamentals for high-quality micro components fabrications. Based on the finite element method (FEM), the simulation model for micromilling of the oxygen-free copper (OFC) was established in this paper. The influences of the key process parameters (feed engagement fz, axial depth of cut ap, radial depth of cut ae, and spindle speed n) on the milling forces were investigated. According to the simulation results, to achieve the minimum undeformed chip thickness, the critical feed engagement was identified to be 2.5 μm/z. when the axial depth of cut increased, the milling force was increasing linearly, but at the same time the milling force took an oscillator decreases due to the increasing of spindle speed. The overall trend of milling force under different radial depths of cut is upward. Therefore, the feed engagement should be greater than 2.5μm/z for micro milling of oxygen-free copper. Small radial depth of cut, small axial depth of cut, and appropriate spindle speed should be selected to obtain a high machining quality. Introduction As an excellent metal with extremely low oxygen content, high conductivity and high corrosion resistance, oxygen-free copper C10100 is widely used in the manufacturing of audio-visual equipment and communication components. With good ductility and no hydrogen embrittlement, it can also be processed into various precision micro parts. Compared with traditional cutting, high-speed micromilling is more suitable for machining micro-small parts. In order to obtain higher dimensional accuracy and better surface quality, it is necessary to study the milling parameters of OFC in the processing of precision parts. In the actual machining process, the changes of milling force caused by the changes of milling parameters can reflect the quality of the final machined parts more intuitively. Therefore, the adjustment of milling parameters can be guided by measuring the milling force in the milling process. In order to reveal the difference in mechanism between traditional cutting and micromilling, scholars have conducted a lot of studies. In the study of cutting poly-crystalling OFC with single crystalline diamond (SOD) micro-tools, X. Ding has proposed that the cutting strategy of reducing cross-feed can improve the cutting performance with using micro-tools. Constant cutting forces, burr size and an improved roughness of the machined surface have been obtained by employing this cutting strategy [1]. Niu has presented an innovative cutting force modeling concept by taking account of micro-cutting dynamics. Experimental cutting trial is conducted to validate the modeling approach and the cutting force model [2]. Qu has studied the impact of MQCL method on the machining results and mechanical properties of the component [3]. Yuan has proposed an innovative uncut chip thickness algorithm and developed the model for determining the instantaneous uncut chip thickness in micro end-milling processes [4]. D.DAS has studied the effect of stress parameters on ratcheting deformation stages of polycrystalline OFHC copper [5]. For the micromilling of pure copper, M. Rahman has studied the failure mechanism and factors which affect the micro end mill [6]. Liu has studied the relationship between size effect and burr in micromilling OFC and constructed a geometric model of exit burrs [7]. Liu has established SPH simulation model and carried out systematic research on formation mechanism of chip [8].For oxygen-free copper materials, Tian has established a constitutive model and carried out simulation analysis based on Abaqus [9]. Cheng has proposed 211

Polyetheretherketone (PEEK) material has attracted extensive attentions and research in the medical field due to its properties similar to biological bones. But there is a lack of cutting forces in PEEK machining. In this paper, the milling simulations and experiments are carried out taking the milling forces as the study index. The results show that the absolute value of the relative error between the simulation results and the experimental ones are less than 5.6%, which testifies the effectiveness of the finite element model. Through the analysis of variance of the orthogonal experimental data, it can be concluded that both the axial depth of cut ap and the radial depth of cut ae have more significant influences on milling forces than the feed engagement fz. The significance order from large to small is the radial depth of cut ap, the axial depth of cut ae, and the feed engagement fz. This study can provide a practical reference for the milling process optimization of the PEEK material.

Antifungal activities of the commercial rice wine extracts of Allium fistulosum were analyzed. Antifungal activities were tested against 7 pathogenic fungi by using agar disc diffusion and tube dilution tests. The results show that the commercial rice wine extracts of Allium fistulosum have strong antifungal activity against Aspergillus brasiliensis ATCC 16404, Candida albicans ATCC 10231, Microsporumcanis ATCC 36299, M. gypseum ATCC 24102, Trichophyton mentagrophytes ATCC 9533, T. rubrum ATCC 28188, and T. tonsurans ATCC 28942. The commercial rice wine extracts of different A. fistulosum parts were found to exhibit significant antifungal activities with the minimal inhibitory concentration (MIC) in the range of 0.2 - 1.0 mg/mL. The antifungal activity of the extracts of different A. fistulosum parts was in the order of AFS (stem) > AFI (plant body) > AFL (leaf) > AFR (root).

The antioxidant and antibacterial activities of commercial rice wine extracts obtained from different plant parts of Allium fistulosum were assayed. The results showed that commercial rice wine extracts of A. fistulosum contained 28.3-95.9 μL/mL allicin and exhibited significant antioxidant and antibacterial activities. The DPPH radical scavenging capacity ranged from 90.2% to 52.1%, and the IC50 value ranged from 14.6 to 26.0 μg/mL. The total phenolic content of wine extracts was 56.4-198.9 mg GAE/g extracts. The TEAC assay of extracts ranged from 6.2 to 15.5 mmol/g extracts. Antibacterial activities were tested against 4 bacteria b y using agar disc diffusion and tube dilution tests. All extracts exhibited antibacterial activities against gram-positive bacteria, such as Bacillus subtilis and Staphylococcus aureus, and gram-negative bacteria, such as Escherichia coli and Pseudomonas aeruginosa. Thus, A. fistulosum wine extracts could be used as natural and functional additives in cooking foods.